The present invention relates to radar warning receivers.
Radar detectors warn drivers of the use of police radar, and the potential for traffic citations if the driver exceeds the speed limit. The FCC has allocated several regions of the electromagnetic spectrum for police radar use. The bands used by police radar are generally know as the X, K and Ka bands. Each relates to a different part of the spectrum. The X and K bands are relatively narrow frequency ranges, whereas the Ka band is a relatively wide range of frequencies. By the early 1990""s, police radar evolved to the point that it could operate almost anywhere in the 1600-megahertz wide Ka band. During that time radar detectors kept pace with models that included descriptive names like xe2x80x9cUltra Widexe2x80x9d and xe2x80x9cSuper Wide.xe2x80x9d More recently, police have begun to use laser (optical) systems for detecting speed. This technology was termed LIDAR for xe2x80x9cLight Detection and Ranging.xe2x80x9d
Radar detectors typically comprise a microwave receiver and detection circuitry that is typically realized with a microprocessor or digital signal processor (DSP). Microwave receivers are generally capable of detecting microwave components in the X, K, and very broad Ka band. In various solutions, either a microprocessor or DSP is used to make decisions about the signal content from the microwave receiver. Systems including a digital signal processor have been shown to provide superior performance over solutions based on conventional microprocessors due to the DSP""s ability to find and distinguish signals that are buried in noise. Various methods of applying DSP""s were disclosed in U.S. Pat. Nos. 4,954,828, 5,079,553, 5,049,885, and 5,134,406, each of which is hereby incorporated by reference herein.
Police use of laser has also been countered with laser detectors, such as described in U.S. Pat. Nos. 5,206,500, 5,347,120 and 5,365.055, each of which is incorporated herein by reference. Products are now available that combined laser detection into a single product with a microwave receiver, to provide comprehensive protection.
The DSP or microprocessor in a modem radar detector is programmable. Accordingly, they can be instructed to manage all of the user interface features such as input switches, lights, sounds, as well as generate control and timing signals for the microwave receiver and/or laser detector. Early in the evolution of the radar detector, consumers sought products that offered a better way to manage the audible volume and duration of warning signals. Good examples of these solutions are found in U.S. Pat. Nos. 4,631,542, 5,164,729, 5,250,951, and 5,300,932, each of which is hereby incorporated by reference, which provide methods for conditioning the response generated by the radar detector.
Methods for conditioning detector response are gaining importance, because there is an increasing number of signals present in the X, K, and Ka bands from products that are completely unrelated to police radar. These products share the same regions of the spectrum and are also licensed by the FCC. The growing number of such signals is rapidly undermining the credibility of radar detector performance. Radar detectors cannot tell the difference between emissions from many of these devices and true police radar systems. As a result, radar detectors are increasingly generating false alarms, effectively xe2x80x9ccrying wolfxe2x80x9d, reducing the significance of warnings from radar detectors.
One of the earliest and most prevalent unrelated Microwave sources is the automatic door system used in many commercial buildings such as supermarkets, malls, restaurants and shopping centers. The majority of these operate in the X-Band and produce signals virtually indistinguishable from conventional X-Band Police Radar. Other than the fact that door opening systems are vertically polarized, vs circular polarization for police radar, there is no distinction between the two that could be analyzed and used by a receiver design.
Until recently, virtually all of the door opening systems were designed to operate in the X-Band. As a result, radar detectors generally announced X-Band alerts far more often than K-Band. As these X-Band xe2x80x98pollutersxe2x80x99 grew in numbers, ultimately 99% of X-Band alerts were from irrelevant sources. X-Band alerts became meaningless. The only benefit that these sources offered the user was some assurance that the detector was actually capable of detecting radar. It also gave the user some intuition into the product""s detection range. To minimize the annoyance to users, most radar detector manufacturers added a filter-like behavior that was biased against X-Band sources. Many also added xe2x80x9cBand priorityxe2x80x9d that was biased against X and in favor of bands that were less likely to contain irrelevant sources such as K, Ka, and Laser. If signals in both X and K Bands were detected, band prioritization would announce K, since it was more likely be a threat to the driver. In the last few years, K-Band door opening systems have also grown in number. This has reduced the significance of the K-Band warning and further undercut the overall benefit to the user of a radar detector.
Another unrelated microwave signal is generated by traffic management systems such as the ARTIMIS manufactured by TRW, used in Cincinnati, Ohio. ARTIMIS Stands for xe2x80x9cAdvanced Regional Traffic Interactive Management and Information Systemxe2x80x9d, and reports traffic flow information back to a central control center. Traffic congestion and other factors are analyzed by the control center. Control center employees use this information to formulate routing suggestions and other emergency information, which they transmit to a large distribution of overhead and roadside signs. In order to collect information on vehicle traffic, a roadside ARTIMIS station transmits an X-Band signal toward cars as they drive by. The ARTIMIS source, unlike the X-Band door opener systems, is distinguishable from police radar as it is not transmitted at a single fixed frequency. As a result, it is possible to differentiate police radar signals from sources such as ARTIMIS, and ignore ARTIMIS sources in newer detectors. Older detectors, however, do not incorporate this feature and could be obsolete in areas where ARTIMIS is in use.
Unrelated Microwave signals are also transmitted by a system called the RASHID VRSS. Rashid is an acronym for Radar Safety Brake Collision Warning System. This electronic device warns heavy trucks and ambulances of hazards in their path. A small number of these RASHID VRSS units have been deployed. They are categorized as a member of the xe2x80x98non-stationaryxe2x80x99 set of unrelated sources. As in the ARTIMIS example, detection of RASHID can be prevented.
Perhaps the biggest source of non-stationary unrelated sources is from other radar detectors. These are sometimes referred to as xe2x80x9cpolluting radar detectors,xe2x80x9d and present a serious threat to some detector products. An early example of this occurred in the mid 1980""s when radar detectors using superhomodyne circuitry became popular. Such detectors leak energy in the. X-Band and K-bands and appeared as police radar to other detectors. A solution to this problem is described in U.S. Pat. No. 4,581,769, which is hereby incorporated by reference in its entirety. A similar problem occurred in the early 1990""s when the Ka band was widened. An unexpected result was that the wider Ka band then also detected harmonics of signals generated by local oscillators within many existing radar detectors. U.S. Pat. No. 5,305,007, which is hereby incorporated by reference in its entirety, describes a method for ignoring these polluting detectors.
At this time, there are very few signal sources that can cause false laser detections in comparison to the substantial list of false microwave signals just described. However there are certain types of equipment that can cause the amplifiers and detection circuitry used in a laser detector to generate a xe2x80x9cfalsexe2x80x9d detect. In particular, certain locations near airports have been demonstrated to cause such problems for various laser detector products. As a result, selected airport environments are examples of stationary signals that produce false laser detections.
As can be appreciated from the foregoing example, as sources of unrelated signals continue to propagate, radar detectors must continually increase in sophistication to filter unrelated sources and accurately identify police radar. Each of these changes and enhancements has the potential effect of obsoleting existing detectors that do not include appropriate countermeasures. Furthermore, some sources, particularly stationary door opener sources, at this time cannot be filtered economically, and thus threaten the usefulness of even the most sophisticated modem radar detector.
During the 1980""s, the functionality of radar detectors expanded into other classes of driver notification. A system was developed that required a special transmitter be placed on emergency vehicles, trains, and other driving hazards. The term xe2x80x98emergency radarxe2x80x99 was coined, and a variety of products were introduced that could detect these transmitters. One such solution was disclosed in U.S. Pat. No. 5,559,508, which is hereby incorporated by reference herein in its entirety. Another system was later introduced offering a larger class of xe2x80x98hazard categoriesxe2x80x99 called the SWS system. Both emergency radar and SWS involve the transmission of microwave signals in the xe2x80x98Kxe2x80x99 band. Such signals are considered to be a part of the group of signal types that are intended to be detected by radar detectors.
A drawback of these warning systems is that stationary transmitters of these signals send the same message to drivers constantly, and become a nuisance during daily commute. This is beneficial to xe2x80x98newxe2x80x99 drivers receiving the message for the first time. However these messages become an annoyance to drivers who follow the same path to work everyday.
Thus, radar detector manufacturers are continually confronted with new problems to solve, due to the variety of different types of unrelated sources and their sheer numbers. The rate at which new or upgraded radar detector models are introduced continues to increase as manufacturers try to evolve their products to manage the growing number of unrelated sources. Meanwhile, the market for radar detectors is shrinking because consumers are no longer interested in buying products that so quickly become obsolete.
The present invention overcomes these difficulties by providing a method of operating a radar detector that aids in the management of unrelated sources, and permitting the detector to dynamically improve its handling of unrelated sources. As noted above, many non-stationary sources can be identified and ignored using existing technology. However, many stationary sources cannot, as yet be effectively filtered economically with existing technology. Accordingly, the invention provides a radar detector that includes technology for determining the location of the detector, and comparing this location to the locations of known stationary sources, to improve the handling of such detections.
In one embodiment, a radar detector may ignore detections received in an area known to contain a stationary source. In the specific embodiment described below, substantially more sophisticated processing is performed to determine whether and what actions to take in response to a detection.
The Global Positioning Satellite System (GPS) offers an electronic method for establishing current physical coordinates very accurately. In the detailed embodiment described below, a radar detector utilizes a GPS system to determine its current position. The detector also maintain a list of the coordinates of the known stationary source xe2x80x9coffendersxe2x80x9d in nonvolatile memory. Each time a microwave or laser source is detected, it will compare its current coordinates to this list. Notification of the driver will take on a variety of forms depending on the setup configuration.
By adding GPS conditioning capabilities to a radar detector, the combination becomes a new product category that is capable of rejecting signals from any given location no matter what the nature of the microwave/laser signals might be from that location. This will have a dramatic effect on the usable life of the product and subsequent value to its owner.